Seeing bright lights in your eyes, known as photopsia, is the sensation of perceiving light flashes when no external light source is present. These visual disturbances occur because the light-sensitive retina or the brain’s visual pathways are stimulated abnormally. The brain interprets these electrical signals as light, whether they appear as sparks, streaks, or zigzag lines. While many causes are harmless and temporary, identifying the origin of these flashes is important because they can sometimes signal a condition requiring prompt medical attention.
Common Temporary Causes
A frequent, non-structural cause of photopsia is the visual aura associated with a migraine. This phenomenon, sometimes called a silent migraine, involves visual disturbances like shimmering, zigzag lines, or flashing dots. The aura is thought to be caused by a wave of altered electrical activity sweeping across the visual cortex in the brain and can last for several minutes up to an hour.
Another common experience is phosphenes, which are flashes induced by mechanical pressure, such as rubbing your eyes vigorously. Applying pressure stimulates the light-sensing cells of the retina, causing them to fire an electrical impulse that the brain interprets as light. These flashes, often described as “seeing stars,” can also be triggered by a sudden blow to the head, a forceful sneeze, or coughing. Phosphenes from these benign events are transient, disappearing quickly once the mechanical stimulation ceases.
Causes Related to the Eye’s Interior Structure
The most frequent origin of photopsia is mechanical stimulation of the retina by the vitreous humor, the clear, gel-like substance filling the center of the eye. As a normal part of aging, the vitreous gel shrinks and liquefies, leading to a separation from the retina called Posterior Vitreous Detachment (PVD). This separation causes the vitreous to tug on the retina, which the brain registers as flashes, often described as lightning streaks or camera flashes in the peripheral vision.
PVD is a common condition, but the traction on the retina can sometimes pull too hard. If the vitreous gel is firmly attached, this tugging can result in a Retinal Tear. A retinal tear is serious because fluid can pass through the opening and accumulate behind the retina, causing a Retinal Detachment. The flashes associated with a tear or detachment tend to be more intense, persistent, and recurrent than those from a simple PVD.
Distinguishing between a PVD and a tear requires a comprehensive eye examination. A retinal detachment prevents the retina from receiving oxygen and nutrients, and if left untreated, it can lead to permanent vision loss. The flashes in these cases are a physical warning sign of a structural problem requiring immediate treatment.
Systemic and Neurological Contributors
Flashes of light can also be a symptom of conditions involving the vascular or nervous system. Sudden changes in blood flow or blood pressure can cause momentary photopsia, sometimes referred to as “seeing stars.” This can occur with a rapid drop in blood pressure, such as when standing up too quickly, or in serious conditions like severe hypertension or preeclampsia during pregnancy.
Head trauma or concussion can induce temporary visual disturbances, including flashes, due to the sudden impact stimulating the visual pathways. Certain medications, including antidepressants and psychotropic drugs, have been noted to occasionally induce photopsia as a side effect. In these systemic cases, treating the underlying medical issue, such as regulating blood pressure or managing medication side effects, resolves the visual symptoms.
Knowing When to Seek Urgent Care
A sudden onset of new or increased flashes should prompt an immediate medical evaluation. Specific “red flag” symptoms that necessitate urgent care include a dramatic increase in the number of floaters, often described as a shower of specks. Flashes accompanied by a shadow or dark curtain moving across any part of the field of vision are particularly concerning.
This “curtain” effect often indicates a Retinal Detachment. A sudden loss of vision, even partial, alongside flashes is also a sign of a serious ocular event. These symptoms require immediate consultation with an eye care specialist, preferably within 24 hours, because a torn or detached retina needs prompt treatment to prevent permanent vision loss.